Catalyst for polyisocyanurate foams made with alternative blowing agents

ABSTRACT

Rigid, closed cell polyisocyanurate foams are prepared by reacting together a polyisocyanate and a polyester polyol or a mixture of a polyester polyol and at least one other isocyanate-reactive compound in the presence of (a) a hydrogen-containing blowing agent or a mixture of a hydrogen-containing blowing agent and at least one co-blowing agent and (b) a catalyst mixture comprising (i) a carboxylate salt of an alkali metal or an alkaline earth metal or mixtures thereof, (ii) a tertiary amine, and (iii) a quaternary ammonium carboxylate salt, wherein the mole ratio of carboxylate metal salt: tertiary amine is a value less than about 2:1, and the total moles of quaternary ammonium carboxylate salt are less than the combined moles of the carboxylate metal salt and the tertiary amine.

This is a division of application Ser. No. 08/224,414, filed Apr. 8,1994 now U.S. Pat. No. 5,405,884, which is a continuation-in-part ofapplication Ser. No. 08/203,183, filed Feb. 28, 1994, abandoned, whichis a division of application Ser. No. 08/062,914, filed May 18, 1993,U.S. Pat. No. 5,308,883, which is a continuation-in-part of applicationSer. No. 07/971,105, filed Nov. 4, 1992, abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the preparation of high temperature resistant,insulating polyisocyanurate foams and is more particularly concernedwith a novel catalyst combination for the preparation of such foams fromcompositions containing polyester polyols and blowing agents used toreplace the conventional fully halogenated chlorofluorocarbons.

2. Description of the Prior Art

It is well known in the manufacture of rigid polyurethane andpolyisocyanurate foams to employ chlorofluorocarbons, such astrichlorofluoromethane, as the blowing agent. These chlorofluorocarboncompounds boil or exhibit a significant vapor pressure at ambienttemperatures and are volatilized during the exothermic reaction of anisocyanate with an active hydrogen-containing compound, such as apolyol. The expanding gas is entrapped within the reaction mixture andforms an insulating cellular structure. While the foam industry has hadgood results using the conventional chlorofluorocarbon blowing agents,such as CFC-11, the agents have come under attack in recent years on theground that they are believed to give rise to environmental problemsconcerned with ozone depletion in the stratosphere. Accordingly, thesearch is ongoing for alternative blowing agents with a low ozonedepletion factor to replace the conventional ones.

It is believed that hydrogenated CFC's (also known as HCFC's), which arepartially halo-substituted hydrocarbons, present less risk than theCFC's. Because the HCFC's contain one or more hydrogen atoms, they morereadily dissociate under conditions encountered in the atmosphere, andtherefore, less of them would reach the ozone layer of the stratospherein a form which could cause significant damage. Accordingly, thehydrogen-containing halocarbons have been investigated as possiblealternatives for CFC-11 in rigid foam applications.

The search for acceptable alternative blowing agents among hydrogenatedCFC's is difficult because of the combination of performancecharacteristics required of them. The agents must not impartunacceptable fire or toxicological risks in the foaming operation or tothe finished foam products. In this regard, it is desirable forpolyisocyanurate foams to develop a thick protective char under fireexposure, but it is found that the char shrinkage for foams made withHCFC's is greater than for identical polymer compositions blown withCFC-11. The agents further must not react with the other components ofthe foam formulation and should be adequately soluble in the foamsystem. Also, their boiling point, vapor thermal conductivity, capacityto efficiently produce gas and diffusion rate must be appropriate forthe formation of highly insulating foams. Finally, the alternativeblowing agents should be reasonable in cost.

There still remains a need for a rigid polyisocyanurate foam which hassuperior properties even though the conventional CFC blowing agents areavoided in its production.

OBJECTS OF THE INVENTION

It is therefore an object of the present invention to provide animproved polyisocyanurate foam from a foam-forming composition whichcontains both a polyester polyol and a blowing agent having reducedozone depletion potential.

It is another object of the present invention to produce an improvedrigid polyisocyanurate foam material having a combination ofadvantageous properties, including a high degree of fire resistance withlow smoke evolution and flame spread on combustion.

It is still another object of the present invention to provide acatalyst blend for the production, from a foam-forming compositioncontaining a polyester polyol and an alternative blowing agent, of apolyisocyanurate foam having a combination of desirable properties,including an appropriate reactivity profile, a reduced friability, gooddimensional stability, and high thermal stability, insulation value andcompressive strength.

It is a further object of the present invention to provide a catalystblend whose use in the production of polyisocyanurate foam contributesto char integrity and minimum char shrinkage when the resultant foam isexposed to fire.

It is a still further object of the present invention to provide closedcell polyisocyanurate foam materials which can be used in buildingpanels which are highly insulating, thermally resistant, soundproof andself-supporting.

BRIEF DESCRIPTION OF DRAWING

The invention will now be described with reference to the accompanyingdrawing which is a side schematic representation of an apparatussuitable for producing a polyisocyanurate form material in accordancewith the present invention.

SUMMARY OF THE INVENTION

The above objects have been achieved through the use of a particularcombination of catalysts for the formation of a rigid polyisocyanuratefoam. The catalyst mixture of the invention comprises a tertiary amine,a metal salt of an organic acid and a quaternary ammonium carboxylatesalt. The proportion of organic acid metal salt to tertiary amine in thecatalyst blend is advantageously less than that conventionally used forthe preparation of rigid polyisocyanurate foams. The catalyst blendsuitably contains about 3-.5, preferably about 2-.5, moles of organicacid metal salt per mole of tertiary amine. It has been found that theuse of this catalyst mixture of the invention results in closed cellpolyisocyanurate foam materials characterized by outstanding properties,including an appropriate reactivity profile, low friability, gooddimensional stability, low flammability, and low thermal conductivity.The catalyst mixture is especially effective through its contribution tothe formation of a protective char when the foam is subjected tocombustion.

The improved polyisocyanurate foam of the invention is prepared fromreactants comprising a polyisocyanate and a polyester polyol, preferablyan aromatic polyester polyol, which are brought together in the presenceof the catalyst mixture and at least one hydrogen atom-containingblowing agent, preferably a hydrogen-containing halocarbon, such asHCFC-141b (1,1,1-dichlorofluoroethane). The foaming reaction may becarried out in the presence of auxiliaries and additives as required(e.g., a surfactant).

The polyisocyanate component employed in the preparation of the cellularpolymers of the invention can be any of the polyisocyanates known to beuseful in the art of polymer formation. A preferred group ofpolyisocyanates are the aromatic polyisocyanates, especiallymethylene-bridged polyphenyl polyisocyanate mixtures.

The polyisocyanate is reacted with a polyol component which comprises apolyester polyol or a mixture of a polyester polyol with at least oneother isocyanate-reactive compound, such as a polyether polyol. Therelative proportions of reactive components are generally such that theequivalent ratio of isocyanate groups to isocyanate reactive groups(e.g., hydroxy groups) is at least about 1.2:1, preferably at leastabout 2:1. In a preferred embodiment of the invention, the polyolcomponent comprises 50 to 100%, by weight, of a polyester polyol,preferably an aromatic polyester polyol. Especially preferred are thecrude polyester polyols obtained by the transesterification of crudereaction residues or scrap polyester resins, as disclosed in U.S. Pat.No. 4,996,242, which disclosure relative thereto is incorporated hereinby reference.

DETAILED DESCRIPTION OF THE INVENTION

The high temperature and fire resistant polyisocyanurate cellularpolymers of the present invention are prepared through the use of anovel catalyst combination of an organic acid metal salt, a tertiaryamine, and a quaternary ammonium carboxylate salt wherein the organicacid metal salt: tertiary amine ratio is lower than the ratio of thesetwo catalyst components which is conventionally used for the formationof rigid polyisocyanurate foams. Through this catalyst combination, ithas been found that the fire performance of polyisocyanurate foams blownwith blowing agents whose flammability exceeds that of CFC-11 isimproved, whereby minimal char shrinkage occurs and char integrity ismaintained upon exposure of the foams to combustion.

The organic acid metal salt of the catalyst mixture suitably is analkali metal and/or alkaline earth metal salt(s) of a carboxylic acid,such as one containing from about 1 to 30 carbon atoms. The cation ofthe organic acid metal salt, which is preferably an alkali metalsalt(s), advantageously is K or Na, more preferably K. Particularlypreferred are C₁ -C₈ carboxylate salts, including the sodium andpotassium salts of formic, acetic, propionic and 2-ethylhexanoic acids.

The tertiary amines which can be employed in the catalyst system inaccordance with the invention are those which are more usually employedto catalyze the reaction between an isocyanato group and an activehydrogen atom. Such catalysts are a group of compounds well recognizedin the art of synthesizing polyurethanes; see, for example, Saunders etal., Polyurethanes, Chemistry and Technology, Part I, pages 228-230,Interscience Publishers, New York, 1964; see also Burkus, J., Journal ofOrganic Chemistry, 26, pages 779-782, 1961.

Representative of said tertiary amine catalysts are:N,N-dialkylpiperazines such as N,N-dimethylpiperazine,N,N-diethylpiperazine and the like; trialkylamines such astrimethylamine, triethylamine, tributylamine and the like;1,4-diazabicyclo[2.2.2]octane, which is more frequently referred to astriethylene diamine, and the lower-alkyl derivatives thereof such as2-methyl triethylene diamine, 2,3-dimethyl triethylene diamine,2,5-diethyl triethylene diamine and 2,6-diisopropyl triethylene diamine;N,N',N"-trialkylaminoalkyl-hexahydrotriazines such asN,N',N"-tris(dimethylaminomethyl)-hexahydrotriazine,N,N',N"tris(dimethylaminoethyl)hexahydrotriazine and the like; mono-,di-, and tri-(dialkylaminoalkyl) monohydric phenols or thiophenols suchas 2-(dimethylaminomethyl)phenol, 2-(dimethylaminobutyl)phenol and thelike; N,N,N',N'-tetraalkylalkylenediamines such asN,N,N',N'-tetramethyl-1,3-propane diamine,N,N,N',N'-tetramethyl-1,3-butanediamine,N,N,N',N'-tetramethylethylenediamine and the like;N,N-dialkylcyclohexylamines such as N,N-dimethylcyclohexylamine,N,N-diethylcyclohexylamine and the like; N-alkylmorpholines such asN-methylmorpholine, N-ethylmorpholine and the like;N,N-dialkylalkanolamines such as N,N-dimethylethanolamine,N,N-diethylethanolamine and the like; N,N,N'N'-tetraalkylguanidines suchas N,N,N',N'-tetramethylguanidine, N,N,N',N'-tetraethylguanidine and thelike. The tertiary amine catalysts can be employed singly or incombination of two or more such amines.

The preferred tertiary aminophenol of the catalyst mixture contains oneor more tertiary amino groups and one or more phenolic hydroxyl groups.A tertiary amino group contained by the tertiary aminophenol may be anytertiary amino group; for example, it can be the group: ##STR1## whereinR₁ and R₂ are alike or unlike, and are each an aliphatic,cycloaliphatic, aryl, heterocyclic, aliphaticcycloaliphatic,aliphatic-aryl, aliphatic-heterocyclic, cycloaliphatic-aliphatic,cycloaliphatic-aryl, cycloaliphatic-heterocyclic, aryl aliphatic, arylcycloaliphatic, aryl heterocyclic, heterocyclic aliphatic,heterocycliccycloaliphatic or heterocyclic aryl group; or R¹ and R₂ arejoined to form an alkylene chain that can be interrupted by aheterocyclic atom. Preferred tertiary amino groups are obtained when R₁and R₂ are each an alkyl, cycloalkyl, phenyl, naphthyl, piperid-4-yl,alkyl cycloalkyl, alkyl phenyl, alkyl naphthyl, 1-alkyl-4-piperidyl,cycloalkyl alkyl, cycloalkyl phenyl, cycloalkyl naphthyl,1-cycloalkyl-3-pyrrolidinyl, phenyl alkyl, naphthyl alkyl, phenylcycloalkyl, 1-phenyl-4-piperidyl, pyrid-4-yl alkyl, pyrrolidin-3-ylcyclohexyl, morpholin-3-yl phenyl, morpholino, pyrrolidino or piperidinogroup. Particularly preferred tertiary amino groups are obtained when R₁and R₂ are each an alkyl group containing 1 to 8 carbon atoms. Ifdesired, the tertiary amino groups can be joined to the phenolic residueby an alkylene group, preferably an alkylene group containing 1 to 8carbon atoms.

Some examples of tertiary aminophenols containing one or more tertiaryamino groups and one or more phenolic hydroxyl groups are:1-hydroxy-2-dialkylamino-4,5-dialkylbenzenes such as1-hydroxy-2-diethylamino-4,5-dimethylbenzene; 1-hydroxy-1-dialkylaminonaphthalenes such as 1-hydroxy-2-dimethylamino naphthalene;1-hydroxy-2,4-bis(dialkylamino)benzenes such as1-hydroxy-2,4-bis(diethylamino)benzene; 1-hydroxy-2-dialkylaminoalkylbenzenes such as 1-hydroxy-2-dimethylaminoethyl benzene;1,2-dihydroxy-3-dialkylaminoalkyl benzenes such as1,2-dihydroxy-3-dimethylaminomethyl benzene; and1,2,3-trihydroxy-5-dialkylaminoalkyl benzenes such as1,2,3-trihydroxy-5-dimethylaminomethyl benzene.

Preferred tertiary aminophenols have the general formula: ##STR2##wherein alk is an alkylene group; and R₃ and R₄ are similar ordissimilar and are each an alkyl group. Particularly preferred tertiaryaminophenols are 2,4,6-tris(dialkylaminoalkyl)phenols, especially thosewherein the alkyl groups have 1 to 8 carbon atoms; as, for example,2,4,6-tris(dimethylaminomethyl)phenol,2,4,6-tris(diethylaminomethyl)phenol, and2,4,6-tris(N-methyl-N-ethylaminoethyl)phenol.

Other preferred tertiary amine catalysts for use in preparingpolyisocyanurate foams of the invention are the triethylene diamines andthe N,N'N"-tris(dialkylaminoalkyl) hexahydrotriazines.

The molar ratio of the organic acid metal salt to the tertiary amine ischosen to optimize the fire performance of the polyisocyanurate foams.The weight loss and volume shrinkage experienced by foams subjected toflammability char tests when the high metal salt: tertiary amine molarratios of the prior art are employed can be significantly lessened bylowering this ratio. The appropriate ratio for any given metalsalt/tertiary amine combination and foam-forming mixture can be readilydetermined through routine experimentation. Generally, the mole ratio ofthe organic acid metal salt to the tertiary amine in the inventivemixture is less than about 3:1, preferably less than about 2.5:1, andmore preferably less than about 2:1. In a particularly desirableembodiment of the invention, the metal salt: tertiary amine mole ratiois about 1.5-1:1 (e.g., 1:1).

The catalyst mixture of the invention includes a quaternary ammoniumcarboxylate salt, which enhances the char structure of burnt foams madewith the mixture. This salt preferably is made from a lower-alkanoicacid containing from 1 to 8 carbon atoms, inclusive, such as formic,acetic, propionic, butyric, pentanoic, hexanoic, heptanoic, octanoic,and isomers thereof. The quaternary substituents may be independentlyselected from the group consisting of lower-alkyl,substituted-lower-alkyl (e.g., hydroxy- or halo-lower-alkyl), andaralkyl. Quaternary salt components of the catalyst mixture and theirpreparation are described in U.S. Pat. No. 3,954,684, which disclosureis incorporated herein by reference.

The three component catalyst mixture is suitably employed in the form ofan anhydrous solution in a polar hydroxylic organic solvent. The solventis preferably a polyol, which desirably is an alkylene diol orpolyalkylene ether diol, e.g., diethylene glycol. It is generallydesirable to dissolve the catalyst components in about the minimumsolvent needed to dissolve the metal-based component, which is the moredifficultly dissolvable component.

The mole ratio of organic acid metal salt:tertiary amine:quaternaryammonium salt for optimum practice of the invention is readilydeterminable. The preferred ratios are those whose use gives rise toreduced foam weight loss, reduced % volume loss and increased chardensification when the foam is subjected to fire testing, such as inaccordance with the Factory Mutual BUR Calorimeter test. The use of theorganic acid metal salt/tertiary amine mixture in the unconventionallower ratio discussed above in combination with the quaternary ammoniumsalt improves considerably the fire performance of the inventivepolyisocyanurate foams made with alternate blowing agents. The moles ofquaternary ammonium salt(s) are advantageously less than the total molesof organic acid metal salt(s) and tertiary amine(s).

The catalyst mixtures of the invention are used in a catalyticallyeffective amount. Generally, the catalyst mixture comprises from about0.1 to 20 and preferably from about 0.3 to 10 weight percent of thetotal foam-forming composition.

The polyisocyanurate foams of the present invention can be prepared byusing standard techniques known to those skilled in the art. These foamscan be simply prepared by polymerizing and foaming the organicpolyisocyanate with the polyol in the presence of the catalyst mixture,blowing agent and other additives, such as a surfactant and the like, asnecessary, at a suitable temperature, such as from about 0° C. to 150°C. The quantities of reactants are such that the ratio of isocyanate(NCO) groups to hydroxyl (OH) groups is generally from 1.2:1 to 10:1 orhigher. This NCO:OH ratio is preferably at least about 1.5:1, morepreferably at least about 3:1, and most preferably at least about 4:1.

The polyisocyanate component employed in the foam preparation can be anyof the polyisocyanates known to be useful in the art of polymerformation. The organic di-or polyisocyanates of the invention includealiphatic, cycloaliphatic, araliphatic, aromatic and heterocyclicpolyisocyanates and combinations thereof characterized in having two ormore isocyanate (NCO) groups per molecule.

Among the many isocyanates suitable for the practice of the subjectinvention are, for example, tetramethylene, hexamethylene, octamethyleneand decamethylene diisocyanates, and their alkyl substituted homologs,1,2-, 1,3- and 1,4-cyclohexane diisocyanates, 2,4- and2,6-methylcyclohexane diisocyanates, 4,4'- and2,4'-dicyclohexyldiisocyanates, 4,4'- and 2,4'-dicyclohexylmethanediisocyanates, 1,3,5-cyclohexane triisocyanates, saturated(hydrogenated) polymethylenepolyphenylenepolyisocyanates,isocyanatomethylcyclohexane isocyanates, isocyanatoethylcyclohexaneisocyanates, bis(isocyanatomethyl)-cyclohexane diisocyanates, 4,4'- and2,4'-bis(isocyanatomethyl) dicyclohexane, isophorone diisocyanate, 1,2-,1,3-, and 1,4-phenylene diisocyanates, 2,4- and 2,6-toluenediisocyanate, 2,4'-, 4,4'- and 2,2-biphenyl diisocyanates, 2,2'-, 2,4'-and 4,4'-diphenylmethane diisocyanates,polymethylenepolyphenylene-polyisocyanates (polymeric MDI), and aromaticaliphatic isocyanates such as 1,2-, 1,3-, and 1,4-xylylenediisocyanates.

Organic isocyanates containing heteroatoms may also be utilized, forexample those derived from melamine. Modified polyisocyanates, such ascarbodiimide or isocyanurate can also be employed. Liquid carbodiimidegroup- and/or isocyanurate ring-containing polyisocyanates havingisocyanate contents from 15 to 33.6 percent by weight, preferably from21 to 31 percent by weight, are also effective, for example, those basedon 4,4'-, 2,4'-, and/or 2,2'-diphenylmethane diisocyanate and/or 2,4-and/or 2,6-toluene diisocyanate, and preferably 2,4- and 2,6-toluenediisocyanate and the corresponding isomer mixtures, 4,4'-, 2,4', and2,2'-diphenylmethane diisocyanates as well as the corresponding isomermixtures, for example, mixtures of 4,4'- and 2,4'-diphenylmethanediisocyanates, mixtures of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates (polymeric MDI), and mixtures of toluenediisocyanates and polymeric MDI. Preferred, however, are the aromaticdiisocyanates and polyisocyanates. Particularly preferred are 2,4-, and2,6-toluene diisocyanate and mixtures thereof (TDI), 2,4'-, 2,2'- and4,4'-diphenylmethane diisocyanate (MDI),polymethylenepolyphenylenepolyisocyanates (polymeric MDI), and mixturesof the above preferred isocyanates.

Most particularly preferred are the polymeric MDI's.

Still other useful organic polyisocyanates are isocyanate terminatedquasi-prepolymers. These quasi-prepolymers are prepared by reactingexcess organic polyisocyanate or mixtures thereof with a minor amount ofan active hydrogen-containing compound. Suitable active hydrogencontaining compounds for preparing the quasi-prepolymers hereof arethose containing at least two active hydrogen-containing groups whichare isocyanate reactive. Typifying such compounds arehydroxyl-containing polyesters, polyalkylene ether polyols,hydroxyl-terminated polyurethane oligomers, polyhydric polythioethers,ethylene oxide adducts of phosphorous-containing acids, polyacetals,aliphatic polyols, aliphatic thiols including alkane, alkene and alkynethiols having two or more SH groups; as well as mixtures thereof.Compounds which contain two or more different groups within theabove-defined classes may also be used such as, for example, compoundswhich contain both an SH group and an OH group. Highly usefulquasi-prepolymers are disclosed in U.S. Pat. No. 4,791,148 and U.S.application Ser. No. 07/342,508, filed Apr. 24, 1989, the disclosures ofwhich with respect to the quasi-prepolymers are hereby incorporated byreference.

The polyester polyols of the invention can be prepared by knownprocedures from a polycarboxylic acid component comprising apolycarboxylic acid or acid derivative, such as an anhydride or ester ofthe polycarboxylic acid, and any polyol component. The polyol componentadvantageously comprises a glycol(s) or a glycol-containing mixture ofpolyols. The polyacid and/or polyol components may, of course, be usedas mixtures of two or more compounds in the preparation of the polyesterpolyols. Particularly suitable polyester polyols for use in the foamproduction are aromatic polyester polyols containing phthalic acidresidues.

The production of the polyester polyols is accomplished by simplyreacting the polycarboxylic acid or acid derivative with the polyolcomponent in a known manner until the hydroxyl and acid values of thereaction mixture fall in the desired range.

After transesterification or esterification, the reaction product can bereacted with an alkylene oxide to form a polyester polyol mixture of theinvention. This reaction desirably is catalyzed. The temperature of thisprocess should be from about 80° to 170° C., and the pressure shouldgenerally range from about 1 to 40 atmospheres.

The polycarboxylic acid component may be aliphatic, cycloaliphatic,aromatic and/or heterocyclic and may optionally be substituted, forexample, by halogen atoms, and/or may be unsaturated. Examples ofsuitable carboxylic acids and derivatives thereof for the preparation ofthe polyester polyols include: oxalic acid; malonic acid; succinic acid;glutaric acid; adipic acid; pimelic acid; suberic acid; azelaic acid;sebacic acid; phthalic acid; isophthalic acid; trimellitic acid;terephthalic acid; phthalic acid anhydride; tetrahydrophthalic acidanhydride; pyromellitic dianhydride; hexahydrophthalic acid anhydride;tetrachlorophthalic acid anhydride; endomethylene tetrahydrophthalicacid anhydride; glutaric acid anhydride; maleic acid; maleic acidanhydride; fumaric acid; dibasic and tribasic unsaturated fatty acidsoptionally mixed with monobasic unsaturated fatty acids, such as oleicacid; terephthalic acid dimethyl ester and terephthalic acid-bis glycolester.

Polyester polyols whose acid component advantageously comprises at leastabout 30% by weight of phthalic acid residues are particularly useful.By phthalic acid residue is meant the group ##STR3## While the aromaticpolyester polyols can be prepared from substantially pure reactantmaterials, more complex ingredients are advantageously used, such as theside-stream, waste or scrap residues from the manufacture of phthalicacid, terephthalic acid, dimethyl terephthalate, polyethyleneterephthalate, and the like. Particularly suitable compositionscontaining phthalic acid residues for use in the invention are (a)ester-containing by-products from the manufacture of dimethylterephthalate, (b) scrap polyalkylene terephthalates, (c) phthalicanhydride, (d) residues from the manufacture of phthalic acid orphthalic anhydride, (e) terephthalic acid, (f) residues from themanufacture of terephthalic acid, (g) isophthalic acid and (h)trimellitic anhydride, and (i) combinations thereof. These compositionsmay be converted by reaction with the polyols of the invention topolyester polyols through conventional transesterification oresterification procedures.

A preferred polycarboxylic acid component for use in the preparation ofthe aromatic polyester polyols is phthalic anhydride. This component canbe replaced by phthalic acid or a phthalic anhydride bottomscomposition, a phthalic anhydride crude composition, or a phthalicanhydride light ends composition, as such compositions are defined inU.S. Pat. No. 4,529,744.

Other preferred materials containing phthalic acid residues arepolyalkylene terephthalates, especially polyethylene terephthalate(PET), residues or scraps.

Still other preferred residues are DMT process residues, which are wasteor scrap residues from the manufacture of dimethyl terephthalate (DMT).The term "DMT process residue" refers to the purged residue which isobtained during the manufacture of DMT in which p-xylene is convertedthrough oxidation and esterification with methanol to the desiredproduct in a reaction mixture along with a complex mixture ofby-products. The desired DMT and the volatile methyl p-toluateby-product are removed from the reaction mixture by distillation leavinga residue. The DMT and methyl p-toluate are separated, the DMT isrecovered and methyl p-toluate is recycled for oxidation. The residuewhich remains can be directly purged from the process or a portion ofthe residue can be recycled for oxidation and the remainder divertedfrom the process, or, if desired, the residue can be processed further,as, for example, by distillation, heat treatment and/or methanolysis torecover useful constituents which might otherwise be lost, prior topurging the residue from the system. The residue which is finally purgedfrom the process, either with or without additional processing, isherein called DMT process residue.

These DMT process residues may contain DMT, substituted benzenes,polycarbomethoxy diphenyls, benzyl esters of the toluate family,dicarbomethoxy fluorenone, carbomethoxy benzocoumarins and carbomethoxypolyphenols. Cape Industries, Inc. sells DMT process residues under thetrademark Terate®101. DMT process residues having a differentcomposition but still containing the aromatic esters and acids are alsosold by DuPont and others. The DMT process residues to betransesterified in accordance with the present invention preferably havea functionality at least slightly greater than 2.

Such suitable residues include those disclosed in U.S. Pat. Nos.3,647,759, 4,411,949, 4,714,717, and 4,897,429, the disclosures of whichwith respect to the residues are hereby incorporated by reference.

The polyester polyols are prepared from the above describedpolycarboxylic acid components and any polyol component. The polyols canbe aliphatic, cycloaliphatic, aromatic and/or heterocyclic. Lowmolecular weight aliphatic polyhydric alcohols, such as aliphaticdihydric alcohols having no more than about 20 carbon atoms are highlysatisfactory. The polyols optionally may include substituents which areinert in the reaction, for example, chlorine and bromine substituents,and/or may be unsaturated. Suitable amino alcohols, such as, forexample, monoethanolamine, diethanolamine, triethanolamine, or the likemay also be used. Moreover, the polycarboxylic acid(s) may be condensedwith a mixture of polyhydric alcohols and amino alcohols.

A preferred polyol component is a glycol. The glycols may containheteroatoms (e.g., thiodiglycol) or may be composed solely of carbon,hydrogen, and oxygen. They are advantageously simple glycols of thegeneral formula C_(n) H_(2n) (OH)₂ or polyglycols distinguished byintervening ether linkages in the hydrocarbon chain, as represented bythe general formula C_(n) H_(2n) O_(x) (OH)₂. In a preferred embodimentof the invention, the glycol is a low molecular weight aliphatic diol ofthe generic formula:

    HO--R--OH

wherein R is a divalent radical selected from the group consisting of:

(a) alkylene radicals each containing from 2 through 6 carbon atoms, and

(b) radicals of the formula:

    --(R.sup.1 O).sub.m --R.sup.1 --

wherein R¹ is an alkylene radical containing from 2 through 6 carbonatoms, and m is an integer of from 1 through 4, and

(c) mixtures thereof.

Examples of suitable polyhydric alcohols include: ethylene glycol;propylene glycol-(1,2) and -(1,3); butylene glycol-(1,4) and -(2,3);hexane diol-(1,6); octane diol-(1,8); neopentyl glycol;1,4-bishydroxymethyl cyclohexane; 2-methyl-1,3-propane diol; glycerin;trimethylolpropane; trimethylolethane; hexane triol-(1,2,6); butanetriol-(1,2,4); pentaerythritol; quinol; mannitol; sorbitol; methylglucoside; diethylene glycol; triethylene glycol; tetraethylene glycoland higher polyethylene glycols; dipropylene glycol and higherpolypropylene glycols as well as dibutylene glycol and higherpolybutylene glycols. Especially suitable polyols are alkylene glycolsand oxyalkylene glycols, such as ethylene glycol, diethylene glycol,dipropylene glycol, triethylene glycol, tripropylene glycol,tetraethylene glycol, tetrapropylene glycol, trimethylene glycol andtetramethylene glycol, and 1,4-cyclohexanedimethanol(1,4-bis-hydroxymethylcyclohexane).

The term "polyester polyol" as used in this specification and claimsincludes any minor amounts of unreacted polyol remaining after thepreparation of the polyester polyol and/or unesterified polyol (e.g.,glycol) added after the preparation. The polyester polyol canadvantageously include up to about 40 weight percent free glycol.

The polyester polyols advantageously have an average functionality ofabout 1.8 to 8, preferably about 1.8 to 5, and more preferably about 2to 2.5. Their hydroxyl number values generally fall within a range ofabout 15 to 750, preferably about 30 to 550, and more preferably about100 to 550, and their free glycol content generally is from about 0 to40, preferably from 2 to 30, and more preferably from 2 to 15, weightpercent of the total polyester polyol component.

Examples of suitable polyester polyols are those derived from PET scrapand available under the designation Terol 235 from Oxid, Chardol 170,336A, 560, 570, 571 and 572 from Chardonol and Freol 30-2150 fromFreeman Chemical. Examples of suitable DMT derived polyester polyols areTerate® 202, 203, 204, 214, 254, 254A and 2541 polyols, which areavailable from Cape Industries. Phthalic anhydride derived-polyesterpolyols are commercially available under the designation Pluracol®polyol 9118 from BASF Corporation, and Stepanpol PS-2002, PS-2352,PS-2402, PS-2502A, PS-2502, PS-2522, PS-2852, PS-2852E, PS-2552, andPS-3152 from Stepan Company. Especially useful polyester polyols areTerol 235, Stepanpol PS-2352 and Terate 214 and 2541.

The polyols which can be employed in combination with polyester polyolsin the preparation of the polyisocyanurate foam compositions of theinvention include monomeric polyols and polyether polyols. Suitablepolyether polyols are the reaction products of a polyfunctional activehydrogen initiator and a monomeric unit such as ethylene oxide,propylene oxide, butylene oxide and mixtures thereof, preferablypropylene oxide, ethylene oxide or mixed propylene oxide and ethyleneoxide. The polyfunctional active hydrogen initiator preferably has afunctionality of 2-8, and more preferably has a functionality of 3 orgreater (e.g., 4-8).

Any suitable hydrogen atom-containing blowing agent can be employed inthe foam compositions of the present invention. The flammability offoams made with these agents generally exceeds that of foams made withCFC-11. However, through the use of the catalyst mixture of theinvention, polyisocyanurate foams blown with such alternative blowingagents are found to be more fire resistant, when subjected to varioustesting procedures known and used in the foam art, in comparison toidentical foam compositions except for the use of conventionalpolyisocyanurate foam catalysts and amounts thereof.

The alternative blowing agents employed in the preparation of theinventive polyisocyanurate foams can be selected from a broad range ofmaterials, including partially halogenated hydrocarbons, ethers, andesters, hydrocarbons, esters, ethers, and the like. Among the usablehydrogen-containing halocarbons are the HCFC's such as1,1-dichloro-1-fluoroethane (HCFC-141b),1,1-dichloro-2,2,2-trifluoroethane (HCFC-123), monochlorodifluoromethane(HCFC-22), 1-chloro-1,1-difluoroethane (HCFC-142b), 1,1-difluoroethane(HCFC-152a), and 1,1,1,2-tetrafluoroethane (HFC-134a).

A wide variety of co-blowing agent(s) can be employed in conjunctionwith the hydrogen-containing halocarbons in preparing the foamcompositions of the invention. Water, air, nitrogen, carbon dioxide,readily volatile organic substances and/or compounds which decompose toliberate gases (e.g., azo compounds) may be used. Typically, theseco-blowing agents are liquids having a boiling point between minus 50°C. and plus 100° C., and preferably between -50° C. and +50° C.

A preferred method for the production of froth foams of the invention isdisclosed in U.S. Pat. No. 4,572,865, whose disclosure is herebyincorporated by reference. In this method, the froth-forming blowingagent can be any material which is inert to the reactive ingredients andeasily vaporized at atmospheric pressure. This frothing agentadvantageously has an atmospheric boiling point of -50° C. to 10° C. Ina desirable embodiment of the invention, a higher boiling blowing agentis used in conjunction with the frothing agent. The former blowing agentadvantageously has an atmospheric boiling point ranging from about 10°to 80° C.

The blowing agents are employed in an amount sufficient to give theresultant foam the desired bulk density which is generally between 0.5and 10, preferably between 1 and 5, and most preferably between 1.5 and2.5, pounds per cubic foot. The blowing agents generally comprise from 1to 30, and preferably comprise from 5 to 20 weight percent of thecomposition. When a blowing agent has a boiling point at or belowambient, it is maintained under pressure until mixed with the othercomponents. Alternatively, it can be maintained at subambienttemperatures until mixed with the other components.

Any suitable surfactant can be employed in the foams of this invention.Successful results have been obtained with silicone/ethyleneoxide/propylene oxide copolymers as surfactants. Examples of surfactantsuseful in the present invention include, among others,polydimethylsiloxane-polyoxyalkylene block copolymers available from theUnion Carbide Corporation under the trade names "Y-10222", "Y-10764","L-5420" and "L-5340", from the Dow Corning Corporation under the tradenames "DC-193" and "DC-5315", and from Goldschmidt Chemical Corporationunder the tradenames "B-8408" and "B-8407". It has been found thatsurfactants such as Y-10764 can contribute significantly to an increasein foam insulation value. Other suitable surfactants are those describedin U.S. Pat. Nos. 4,365,024 and 4,529,745 and supplied by SlossIndustries Corporation under the trademarks Foamstab 100 and 200.Generally, the surfactant comprises from about 0.05 to 10, andpreferably from 0.1 to 6, weight percent of the foam-formingcomposition.

Other additives may also be included in the foam formulations. Includedare processing aids, viscosity reducers, such as1-methyl-2-pyrrolidinone, propylene carbonate, nonreactive and reactiveflame retardants, such as tris(2-chloroethyl)-phosphate, dispersingagents, plasticizers, mold release agents, antioxidants, compatibilityagents, and fillers and pigments (e.g., carbon black). The use of suchadditives is well known to those skilled in the art.

The present invention also provides a process for producing a laminatewhich comprises (a) contacting at least one facing sheet with afoam-forming mixture comprising the polyisocyanate, polyester polyol,blowing agent, catalyst mixture, and auxiliaries and additives asrequired (e.g., a surfactant), and (b) foaming the foam-forming mixture.The process is advantageously conducted in a continuous manner bydepositing the foam-forming mixture on a facing sheet being conveyedalong a production line, and preferably placing another facing sheet onthe deposited mixture. The foam-forming mixture is convenientlythermally cured at a temperature from about 20° C. to 150° C. in asuitable apparatus, such as an oven or heated mold. Both free rise andrestrained rise processes, such as disclosed in U.S. Pat. No. 4,572,865,may be employed in the foam production.

Any facing sheet previously employed to produce building panels can beemployed in the present invention. Examples of suitable facing sheetsinclude, among others, those of kraft paper, aluminum, glass mats, glassreinforced organic felts, and asphalt impregnated felts, as well aslaminates of two or more of the above.

The foam materials of the invention can also be used, with or without afacer(s), for pipe insulation.

The foam materials of the invention can contain various reinforcementmaterials, such as a quantity of glass fibers, as described in U.S. Pat.Nos. 4,118,533 and 4,284,683, the disclosures of which are herebyincorporated by reference.

It is common practice in the manufacture of the rigid cellularpolyisocyanurates to utilize two preformulated components, commonlycalled the A-component and the B-component. Typically, the A-componentcontains the isocyanate compound that must be reacted with the polyol ofthe B-component to form the foam, and the remaining foam-formingingredients are distributed in these two components or in yet anothercomponent or components.

One method of utilizing the catalyst mixture in the foam-forming processof the invention can be illustrated with reference to the apparatusshown in the drawing. The apparatus includes tanks 10, 11 and 12 forcontaining the foamable ingredients and additives such as isocyanate,polyol, filler, surfactant, dye, blowing agent, etc. The tanks arecharged with the foam-forming mixture in whatever manner is convenientand preferred for the given mixture. For instance, the foam-formingmixture can be divided into three liquid components, with thepolyisocyanate and surfactant in tank 10, the polyol in tank 11, thecatalyst mixture in tank 12, and the blowing agent in tank 10 or 11 ordivided between these tanks, each tank respectively connected to outletlines 13, 14 and 15. When water is used as a co-blowing agent, it isconveniently added to tank 11 or introduced into polyol line 14. Thetemperatures of the ingredients are controlled to ensure satisfactoryprocessing. The lines 13, 14 and 15 form the inlet to metering pumps 16,17 and 18. The apparatus is also provided with a storage tank (notshown) for a frothing agent. This tank discharges into conduit 19 whichopens at " T"-intersection 20 into line 13. A check valve 21 and ballvalve 22 in conduit 19 ensure no backup of material toward the frothingagent storage tank. The frothing agent instead can be introduced in thesame way into line 14 or both lines 13 and 14. The pumps 16, 17 and 18discharge respectively through lines 23, 24 and 25. Lines 24 and 25comprise branches which open into line 26, and lines 23 and 26 are inturn respectively connected to flexible lines 27 and 28. The flexiblelines 27 and 28 discharge to mixing head 29. The apparatus is alsoprovided with a roll 30 of lower facing material 31, and a roll 30' ofupper facing material 31'. Where only a lower facing material is used,the upper facing material can be replaced with a web coated with arelease agent. The apparatus is also provided with metering rolls 32 and33, and an oven 34 provided with vents 35 and 35' for introducing andcirculating hot air. The apparatus also includes pull rolls 36 and 37,each of which preferably has a flexible outer sheath 38 and 39, andcutting means 40a for cutting off side excess material and 40b forsevering the faced foam plastic produced into finite lengths, therebyproducing discrete panels.

As an example of the operation, tank 10 is charged with the organicpolyisocyanate admixed with the surfactant, tank 11 is charged with thepolyol, and tank 12 is charged with the catalyst composition. Theblowing agent may be charged to tank 10 or tank 11, or divided betweenthese tanks. The speeds of the pumps 16, 17 and 18 are adjusted to givethe desired ratios of the ingredients contained in the tanks 10, 11 and12, whereupon these ingredients pass respectively into lines 13, 14 and15. When used, a frothing agent is injected into line 13 upstream ofmetering pump 16. The ingredients pass through lines 23, 24 and 25, aswell as lines 26, 27 and 28, whereupon they are mixed in the mixing head29 and deposited therefrom. By virtue of rotation of the pull rolls 36and 37, the lower facing material is pulled from the roll 30, whereasthe upper facing material is pulled from the roll 30'. The facingmaterial passes over idler rollers such as idler rollers 41 and 42 andis directed to the nip between the rotating metering rolls 32 and 33.The mixing head 29 is caused to move back and forth, i.e., out of theplane of the drawing by virtue of its mounting on a reciprocating means43. In this manner, an even amount of material can be maintainedupstream of the nip between the metering rolls 32, 33. The compositestructure at this point comprising lower and upper facing material 31and 31' having therebetween a foamable mixture 44 now passes into theoven 34 and on along the generally horizontally extending conveyor.While in the oven 34, the core expands under the influence of heat addedby the hot air from vents 35 and 35' and due to the heat generated inthe exothermic reaction between the polyol and isocyanate in thepresence of the catalyst. The temperature within the oven is controlledby varying the temperature of the hot air from vents 35, 35' in order toensure that the temperature within the oven 34 is maintained within thedesired limits of 100° F. to 300° F., and preferably 175° F. to 250° F.The foam, under the influence of the heat added to the oven, cures toform faced foam plastic 45. The product 45 then leaves the oven 34,passes between the pull rolls 36 and 37, and is cut by side edge andlength cutting means 40a and 40b into finite lengths, thereby formingdiscrete panels 46 and 46' of the product.

The particular apparatus described above is especially suitable for themanufacture of structural laminates having a thickness equal to or lessthan 2 inches. When the apparatus makes product within this thicknessrange, the amount of the catalyst mixture is readily adjustable toprovide a suitable foam reactivity profile, e.g., a cream time of 15-20seconds or less, for the production of structural laminatescharacterized by a broad range of desirable properties. The productionof thicker foam product on this apparatus could result in theincorporation of insufficient catalyst and a product without adequateresistance to shrinkage at cold temperatures. Thicker product could bemanufactured if the apparatus were modified to allow for a suitablereactivity profile.

Numerous other modifications to the above-described apparatus will beimmediately apparent to those skilled in the art. For example, the tanks10, 11 and 12 can be provided with refrigeration means in order tomaintain the reactants at subambient temperatures. In one modification,a frothing agent is not delivered into lines 13 or 14, but is admixedwith the foam-forming ingredient(s) in tanks 10 and/or 11. This approachis especially advantageous for handling large amounts of a highlyvolatile frothing agent, which can, for example, be apportioned in tanks10 and 11 which are specially adapted (e.g., pressurized) to hold thefrothing agent-containing formulations.

As shown in the drawing, a reinforcing web 47 can be fed into theapparatus. Fiberglass fibers constitute a preferred web material. Forexample, in a preferred embodiment the reinforcing web will be the typeof glass mat used in producing the structural laminate of U.S. Pat. No.4,028,158, i.e., a thin mat of long, generally straight glass fibers. Inaccordance with this embodiment, a thin mat 47 of glass fibers is fedfrom roll 48 toward the nip between the two rotating metering rolls 32and 33. By virtue of rotation of the pull rolls 36 and 37, reinforcingmat 47 is pulled from its roll, through the nip of the metering rollsand downstream to form part of the resulting structural laminate.

The invention is further illustrated by the following examples in whichall parts and percentages are by weight unless otherwise indicated.

EXAMPLE 1

This example illustrates the use of the catalyst mixture of theinvention in the synthesis of a polyisocyanurate foam (14% trimer) madefrom a polyester polyol and an alternative blowing agent.

In the foam synthesis, the following quantities of the followingingredients were combined as indicated:

    ______________________________________                                        Item      Ingredient     Parts by Weight                                      ______________________________________                                        A         Polymethylene poly-                                                                          202                                                            phenyl isocyanate.sup.1                                             B         HCFC-141b.sup.2                                                                              39                                                   C         Silicone surfactant.sup.3                                                                    2.2                                                  D         Polyester polyol.sup.4                                                                       98                                                   E         Catalyst.sup.5 12.6                                                 ______________________________________                                         .sup.1 Item A is a polymethylene polyphenyl isocyanate having an              equivalent weight of 138, an acidity of 0.02% HCl, and a viscosity of         2,000 centipoises at 25° C., and is available from Miles Inc. unde     the trade name MONDUR MR200.                                                  .sup.2 Item B is that supplied by ElfAtochem North America.                   .sup.3 Item C is that supplied by OSi Incorporated, Inc. under the trade      name Y10764.                                                                  .sup.4 Item D is an aromatic polyester polyol having an equivalent weight     of 213 and a viscosity at 25° C. of 15,400 cps., and is supplied b     Cape Industries under the trade name Terate 214.                              .sup.5 Item E is a mixture employed in the form of a solution in              polyethylene glycol (PEG200) in a 1:1:1:2 weight ratio of potassium           octoate (70% in diethylene                                                    glycol):2,4,6tris[dimethylaminomethyl]phenol:Nhydroxy-isopropyl trimethyl     ammonium salt of formic acid:PEG200, respectively.                       

Items A, B and C were introduced into a reaction vessel. Item D was thenadded to the vessel, and all ingredients were mixed at 3600 rpm for 10seconds. Item E was then mixed into the contents of the vessel. Allingredients were thereafter mixed at 3600 rpm for an additional 10seconds and then poured into a box, yielding a polyisocyanurate foam.

The foam produced had the reactivity profile, density and closed cellcontent shown in the following Table I. When subjected to Char and HotPlate Tests, the foam was found to undergo the % weight and volumelosses recorded in the table and to develop a thick, dense char uponcombustion, indicating a high degree of fire resistance.

                  TABLE I                                                         ______________________________________                                        FOAM PROPERTIES                                                               ______________________________________                                        Firm/Cream time ratio   1.85                                                  Density, pcf            2.03                                                  Closed cells, %         88.28                                                 Burner Char Test                                                              (2" × 2" × 1" foam sample)                                        % weight loss           66.34                                                 % volume loss          +8.32 (gain)                                           Hot Plate Test          17.82                                                 (4" × 4" × 1" foam sample)                                        % weight loss                                                                 ______________________________________                                    

EXAMPLE 2

This example illustrates the use of the catalyst mixture of theinvention in the synthesis of another polyisocyanurate foam (14% trimer)made from a polyester polyol and an alternative blowing agent.

The foam synthesis was conducted in the manner described in Example 1,utilizing the following quantities of the following ingredients:

    ______________________________________                                        Item      Ingredient     Parts by weight                                      ______________________________________                                        A         Polymethylene poly-                                                                          202                                                            phenyl isocyanate.sup.1                                             B         HCFC-141b.sup.2                                                                              40                                                   C         Silicone surfactant.sup.3                                                                    2.2                                                  D         Polyester polyol.sup.4                                                                       98                                                   E         Catalyst.sup.5 12.6                                                 ______________________________________                                         .sup.1 Of Example 1.                                                          .sup.2 Of Example 1.                                                          .sup.3 Of Example 1.                                                          .sup.4 Item D is an aromatic polyester polyol having an equivalent weight     of 211 and a viscosity at 25° C. of 8,800 cps., and is supplied by     Oxid, Inc. under the trade name Terol 235.                                    .sup.5 Of Example 1.                                                     

The foam had the reactivity profile, density and closed cell contentshown in the following Table II. Char and Hot Plate Tests revealed theformation of a dense char upon combustion of the foam and the % weightand volume losses recorded in the table, indicating a high resistance toheat and flame spread.

                  TABLE II                                                        ______________________________________                                        FOAM PROPERTIES                                                               ______________________________________                                        Firm/Cream time ratio   1.64                                                  Density, pcf            2.00                                                  Closed cells, %         88.58                                                 Burner Char Test                                                              (2" × 2" × 1" foam sample)                                        % weight loss           71.08                                                 % volume loss          +1.04 (gain)                                           Hot Plate Test          18.76                                                 (4" × 4" × 1" foam sample)                                        % weight loss                                                                 ______________________________________                                    

EXAMPLE 3

This example illustrates the production of structural laminates ofpolyisocyanurate foam (12% trimer) with the use of the catalyst mixtureof the invention by reference to the drawing.

The structural laminates were prepared from the ingredients andquantities thereof shown in the following Table III. A free-rise processwas employed. For each of the structural laminates, the A-component wascharged to tank 10, the B-component to tank 11 and the C-component totank 12. The laminates A and B utilized aluminum foil/kraftpaper/aluminum foil facings.

In both cases, components A, B and C were brought together in a highpressure impingement foam head 29 in the proportions shown in the table.Top and bottom facings were fed toward the nip of metering rolls 32 and33. The foam forming mixture was deposited onto the lower facing 31 andmetered between the nip rolls to establish the final product thickness.The laminates proceeded through oven 34 to yield foam boards A and B.

The properties shown in Table III reveal that polyisocyanurate foamlaminates having overall good properties, including superior fireresistance, can be obtained by using the catalyst mixture of theinvention even though the foams were blown wholly by the alternativeblowing agent HCFC-141b.

                  TABLE III                                                       ______________________________________                                        PRODUCTION OF STRUCTURAL LAMINATES                                            INGREDIENTS       12% TRIMER FOAMS                                            (pts by wt)       A          B                                                ______________________________________                                        A-Component                                                                   Polymethylene polyphenyl                                                                        190        189                                              isocyanate.sup.1                                                              HCFC-141b.sup.2    11         16                                              Silicone surfactant.sup.3                                                                        2.2        2.2                                             B-Component                                                                   Polyester polyol  110.sup.4  111.sup.5                                        HCFC-141b.sup.2    29.5       24.5                                            C-Component        7          8                                               Catalyst.sup.6                                                                FOAM PROPERTIES                                                               Firm/Cream time ratio                                                                            1.8        2.0                                             Density, pcf       1.93       1.82                                            Closed cells, %    86.20      85.34                                           ASTM E-84          24         25                                              Flame spread                                                                  Smoke              55         33                                              Compressive strength, psi                                                                        23         17                                              k-factor (ASTM C-518)                                                                            0.138      0.137                                           189 days                                                                      ______________________________________                                         .sup.1 Of Example 1.                                                          .sup.2 Of Example 1.                                                          .sup.3 Of Example 1.                                                          .sup.4 Polyester polyol = aromatic polyester polyol having an equivalent      weight of 213 and a viscosity at 25° C. of 16,600 cps., and is         supplied by Cape Industries under the trade name Terate 214.                  .sup.5 Polyester polyol = aromatic polyester polyol having an equivalent      weight of 218 and a viscosity at 25° C. of 8,800 cps., and is          supplied by Oxid, Inc. under the trade name Terol 235.                        .sup.6 Of Example 1.                                                     

EXAMPLE 4

This example illustrates the production of a polyisocyanurate foamroofing product (14% trimer) with the use of the catalyst mixture of theinvention.

The roofing product was manufactured from the ingredients and quantitiesthereof shown in the following Table IV. A restrained rise process wasemployed. The facers consisted of a glass fiber reinforced organic felt.

During manufacture, the A, B and C components were brought together in alow pressure mechanical foam head and deposited on the bottom facer. Thematerial was fed into an oven by a conveyor and allowed to rise until itwas restricted by the upper platen.

The properties shown in Table IV reveal that the polyisocyanurate foamroofing product has good overall properties, including superior fireresistance, when the catalyst mixture of the invention was used eventhough the foam was blown wholly with HCFC-141b.

                  TABLE IV                                                        ______________________________________                                        PRODUCTION OF ROOFING PRODUCT (14% TRIMER)                                    INGREDIENTS                                                                   (pts by wt)                                                                   ______________________________________                                        A-Component                                                                   Polymethylene polyphenyl                                                      isocyanate.sup.1      201                                                     HCFC-141b.sup.2       24.5                                                    Silicone surfactant.sup.3                                                                           2.2                                                     B-Component                                                                   Polyester polyol.sup.4                                                                              99                                                      HCFC-141b.sup.2       20.5                                                    C-Component           12.7                                                    Catalyst.sup.5                                                                FOAM PROPERTIES                                                               Firm/Cream time ratio 3.0                                                     Density, pcf          1.98                                                    Compressive strength, psi                                                                           30                                                      k-factor (ASTM C-518) .170                                                    194 days                                                                      Factory Mutual BUR Calorimeter                                                                      PASS at 1.5"                                            ______________________________________                                         .sup.1 Of Example 1.                                                          .sup.2 Of Example 1.                                                          .sup.3 Of Example 1.                                                          .sup.4 Of Example 2.                                                          .sup.5 A mixture employed in the form of a solution in polyethylene glyco     (PEG200) in a 2:1:1:1:2 weight ratio of potassium octoate (70% in             diethylene glycol):2,4,6tris[dimethylaminomethyl]                             phenol:N,NDimethyl-cyclohexylamine:N-hydroxyisopropyl trimethyl ammonium      salt of formic acid:PEG200, respectively.                                

We claim:
 1. A closed cell, rigid polyisocyanurate foam which comprisesthe reaction product of (1) a polyisocyanate and (2) a polyester polyolor a mixture of a polyester polyol and at least one otherisocyanate-reactive compound in the presence of (a) ahydrogen-containing blowing agent or a mixture of a hydrogen-containingblowing agent and at least one co-blowing agent, and (b) a catalyticallyeffective amount of a catalyst mixture comprising (i) a salt of acarboxylic acid selected from the group consisting of an alkali metalsalt and an alkaline earth metal salt and mixtures thereof, (ii) atertiary amine, and (iii) a quaternary ammonium carboxylate salt,wherein the mole ratio of carboxylate metal salt: tertiary amine is avalue less than about 2:1, and the total moles of quaternary ammoniumcarboxylate salt are less than the combined moles of the carboxylatemetal salt and the teritary amine.
 2. A laminate comprising at least onefacing sheet adhered to the polyisocyanurate foam of claim
 1. 3. Aprocess for producing a laminate comprising (a) contacting at least onefacing sheet with the foam-forming composition of claim 1, andthereafter foaming and curing the foam-forming composition.
 4. The foamof claim 2 wherein the blowing agent is selected from the groupconsisting of 1,1-dichloro-1-fluoroethane, monochlorodifluoromethane,1-chloro-1,1-difluoroethane, 1,1-difluoroethane,1,1,1,2-tetrafluoroethane and mixtures thereof.
 5. The foam of claim 1wherein the blowing agent is 1,1-dichloro-1-fluoroethane.
 6. The foam ofclaim 1 wherein the mole ratio of the carboxylate metal salt: tertiaryamine is about 1.5-1:1.
 7. The foam of claim 1 wherein component (i) isan alkali metal salt of a carboxylic acid and component (ii) is atertiary aminophenol.
 8. The foam of claim 7 wherein the three catalyticcomponents are contained in a polar hydroxylic organic solvent.
 9. Thefoam of claim 1 wherein the three catalytic components are potassiumoctoate, 2,4,6-tris[dimethylaminomethyl]phenol and theN-hydroxy-isopropyl trimethyl ammonium salt of formic acid.
 10. The foamof claim 9 wherein the mole ratio of potassiumoctoate:2,4,6-tris[dimethylaminomethyl]phenol is about 1:1.
 11. The foamof claim 9 wherein the three catalytic components are contained in asolvent selected from the group consisting of an alkylene diol, apolyalkylene ether diol and mixtures thereof.
 12. The foam of claim 1wherein the polyester polyol is an aromatic polyester polyol.
 13. Thefoam of claim 12 wherein the aromatic polyester polyol is the reactionproduct of a polycarboxylic acid component and an aliphatic diol of theformula:

    HO--R--OH

wherein R is a divalent radical selected from the group consisting of:(a) alkylene radicals each containing from 2 through 6 carbon atoms, and(b) radicals of the formula:

    --(R.sup.1 O).sub.m --R.sup.1 --

wherein R¹ is an alkylene radical containing from 2 through 6 carbonatoms, and m is an integer of from 1 through 4, and (c) mixturesthereof.
 14. The foam of claim 13 wherein the acid component of thearomatic polyester polyol is selected from the group consisting of (a)ester-containing by-products from the manufacture of dimethylterephthalate, (b) scrap polyalkylene terephthalates, (c) phthalicanhydride, (d) residues from the manufacture of phthalic acid orphthalic anhydride, (e) terephthalic acid, (f) residues from themanufacture of terephthalic acid, (g) isophthalic acid, (h) trimelliticanhydride, and (i) combinations thereof.
 15. The foam of claim 12wherein component (i) is an alkali metal salt of a carboxylic acid andcomponent (ii) is a tertiary aminophenol.
 16. The foam of claim 15wherein the mole ratio of the carboxylate alkali metal salt:tertiaryaminophenol is about 1.5-1:1.
 17. The foam of claim 15 wherein theblowing agent is selected from the group consisting of1,1-dichloro-1-fluoroethane, monochlorodifluoromethane,1-chloro-1,1-difluoroethane, 1,1-difluoroethane,1,1,1,2-tetrafluoroethane and mixtures thereof.
 18. The foam of claim 15wherein the blowing agent is 1,1-dichloro-1-fluoroethane.
 19. The foamof claim 15 wherein the mole ratio of the carboxylate alkali metalsalt:tertiary aminophenol is about 1:1.
 20. The foam of claim 15 whereinthe three catalytic components are potassium octoate,2,4,6-tris[dimethylaminomethyl]phenol and the N-hydroxy-isopropyltrimethyl ammonium salt of formic acid, and the catalytic components arecontained in a solvent selected from the group consisting of an alkylenediol, a polyalkylene ether diol and mixtures thereof.
 21. The foam ofclaim 20 wherein the acid component of the aromatic polyester polyol isselected from the group consisting of (a) ester-containing by-productsfrom the manufacture of dimethyl terephthalate, (b) scrap polyalkyleneterephthalates, and (c) combinations thereof.